This invention relates to an improved machine for continuously casting molten metal of the type having at least one thin, endless, flexible casting belt, such as in a twin-belt caster or wheel and belt caster, and more particularly to the method and apparatus for elevation of the temperature of the endless casting belt as it is revolved around the input pulley or nip roll (nip pulley) of the machine by applying steam directly to the reverse surface of the belt through wrap-around steam feed tubes with radial ports therein and a nozzle on one end thereof directing steam against the reverse side of the casting belt closely before it enters the casting zone from the input pulley.
U.S. Pat. No. 3,937,270 entitled "Twin-Belt Continuous Casting Method Providing Control of the Temperature Operating Conditions at the casting Belts" and U.S. Pat. No. 4,002,197 entitled "Continuous Casting Apparatus Wherein the Temperature of the Flexible Casting Belts in Twin-Belt Machines is Controllably Elevated Prior to Contact With the Molten Metal" by R. W. Hazelett and J. F. B. Wood which are assigned to the same assignee as the present application and divisional U.S. Pat. Nos. 4,062,235 and 4,082,101 describe twin-belt continuous casting machines in which the temperature of the flexible casting belts is controllably elevated prior to contact with the molten metal to improve the casting conditions in the operation of the twin, thin, flexible casting belts. The casting belts revolve around pulleys and pass along a casting zone from its input end to its output end with the input pulleys being referred to as the nip or input pulleys or nip rolls. The preheating of the casting belt is provided in the aforesaid patents by the use of infrared heaters which are directed at close range toward the casting surfaces of the belts. These heaters serve to cure and dry any coating material on the belts as well as preheating the belts to lessen the differential temperature that would result between a cold belt suddenly coming into contact with the hot molten metal which is to be cast against the traveling belt. Other methods of preheating the casting belt are also illustrated or mentioned which include heating of hollow nip rolls themselves by injecting hot fluid such as steam which is directed into the interior of the hollow nip roll or directing hot fluid, such as steam into deep grooves in the nip roll beneath the rear surfaces of the casting belts to aid in elevating and controlling their temperature. The difficulty with these procedures is that heating the nip rolls or directing steam into the deep grooves of the nip rolls dissipates a good deal of the heat generated by the steam and applies much of such heat to the input or nip pulley and not to the undersurface of the belt which is directly involved in the casting process. Furthermore, the control of the temperature of the belt relies more on the temperature of the input or nip pulley, and accordingly is not nearly so effective in controlling the actual differential temperature between the belt before and after it enters the casting zone. Moreover, the input or nip pulley is relatively massive and slow to respond in temperature changes; whereas quick response in belt preheating is required as the casting speed is increased during changes in operating conditions in a flexible belt casting machine.